Field of the Invention
The present invention relates generally to a pressure diaphragm for measuring fluid pressure in a line, and more particularly to a pressure diaphragm contained in a disposable cassette containing a fluid pump thereon, which disposable cassette is for installation onto and use with a main pump unit including a pressure transducer therein, which pressure transducer interfaces with the pressure diaphragm in the cassette to measure outlet side pressure in the cassette.
In the past there have been two primary techniques which have been used to deliver drugs which may not be orally ingested to a patient. The first such technique is through an injection, or shot, using a syringe and needle which delivers a large dosage at relatively infrequent intervals to the patient. This technique is not always satisfactory, particularly when the drug being administered is potentially lethal, has negative side effects when delivered in a large dosage, or must be delivered more or less continuously to achieve the desired therapeutic effect. This problem results in smaller injections being given at more frequent intervals, a compromise approach not yielding satisfactory results.
Alternatively, the second technique involves administering a continuous flow of medication to the patient, typically through an IV bottle. Medication may also be delivered through an IV system with an injection being made into a complex maze of IV tubes, hoses, and other paraphernalia. With drop counters being used to meter the amount of bulk fluid delivered, many medications still end up being administered in a large dosage through an injection into the IV lines, although the medications may be diluted somewhat by the bulk fluid.
As an alternative to these two techniques of administering medication to a patient, the relatively recent addition of medication infusion pumps has come as a welcome improvement. Medication infusion pumps are utilized to administer drugs to a patient in small, metered doses at frequent intervals or, alternatively, in the case of some devices, at a low but essentially continuous rate. Infusion pump therapy may be electronically controlled to deliver precise, metered doses at exactly determined intervals, thereby providing a beneficial gradual infusion of medication to the patient. In this manner, the infusion pump is able to mimic the natural process whereby chemical balances are maintained more precisely by operating on a continuous time basis.
One of the requirements of a medication infusion system is dictated by the important design consideration of disposability. Since the portion of the device through which medication is pumped must be sterile, in most applications of modern medication infusion equipment some portions of the equipment are used only once and then disposed of, typically at regular intervals such as once daily. It is therefore desirable that the fluid pump portion of the infusion pump device be disposable, with the fluid pump being designed as an attachable cassette which is of inexpensive design, and which is easily installable onto the main pump unit.
It will be perceived that it is desirable to have a simple disposable cassette design to minimize the cost of construction of the cassette, using the minimum number of parts necessary in the design of the cassette. The design of the cassette must be mass producible, and yet result in a uniform cassette which is capable of delivering liquid medication or other therapeutic fluids with a high degree of accuracy. The cassette should include therein more than just a fluid pump; other features which have formerly been included in peripheral devices may be included in the cassette.
It is the primary objective of the present invention to provide a pressure diaphragm in a disposable cassette for use with a main pump unit. A pressure diaphragm must be integrally contained in the disposable cassette, and not an add-on type such as those known in the art. Such a pressure diaphragm must be of a design retaining all of the advantages of such devices known in the past, and must in addition provide a number of additional advantages and improvements. Specifically, the cassette of the present invention shall provide a pressure diaphragm affording a high degree of precision and accuracy, with the degree of precision remaining constant throughout the life of the cassette. A pressure diaphragm in a cassette must also provide an accurate measurement of downstream pressure, and not be significantly affected by other operating components of the cassette.
The pressure diaphragm must be able to operate with various different cassettes, particularly cassettes operating over a wide range of volume rates. The pressure diaphragm must not interfere with such important cassette features a the ability to gravity flow fluid through the device, and safeguards which prevent accidental flow through the cassette when it is removed from the main pump unit. The pressure diaphragm must operate in conjunction with a sensor installed on the main pump unit, and the interface therebetween must be uniform and consistent to ensure that the pressure diaphragm in every disposable cassette will operate properly.
The inclusion of a pressure diaphragm with the objects and features described above must not result in additional parts being utilized in the design of the disposable cassette, all of the parts must of course be of inexpensive construction, and yet afford the assembled cassette the high degree of accuracy which must be retained. The pressure diaphragm of the present invention must be of a design which enables it to compete economically with known competing systems. It must provide an ease of use rivaling the best of such competing systems, with the installation of a cassette containing the pressure diaphragm being both simple and convenient. The pressure diaphragm shall provide the advantages mentioned above, which are not all contained in any competing design. It must accomplish all these objects in a manner which will retain all of the advantages of reliability, durability, and safety of operation. The pressure diaphragm of the present invention must provide all of these advantages and overcome the limitations of the background art without incurring any relative disadvantage. All the advantages of the present invention will result in a superior medication infusion system having a number of advantages making the system a highly desirable alternative to systems presently available.